1. Technical Field
The present invention relates to gas cooking units. In particular, it relates to automatic shutoff mechanisms for gas grills which reduce loss of fuel and improve safety by automatically shutting off the gas supply based on a preselected pattern of activity.
2. Background Art
The prior art has produced many types of gas cooking devices, such as outdoor barbeque (BBQ) grills, indoor grills, gas kitchen stoves, etc. Potential problems associated with gas fueled cooking devices (hereinafter collectively referred to as grills) are caused when a user forgets to turn off a grill after use. Forgetting to turn off a grill leads to both safety hazards and poor fuel economy.
The prior art has provided a number of devices related to safety. For example, it is known that flame detectors can be installed in a stove to detect if the flame has been extinguished. Once it has been determined that a flame is out, the gas supply is cut off. The purpose of this device is to prevent the situation where a flame inadvertently extinguishes, resulting in a build-up of gas and a subsequent explosion. This type of device is not useful for preventing fires which are caused by grills that are left unattended and continue to heat up until a fire is started.
Attempts to improve safety have included remote controlled ignition systems which allows a BBQ grill to be ignited with the grill lid closed. This safety feature is related to starting the grill and does not address the concerns related to grills which are inadvertently left on. A variation of this system prevents the grill from lighting if the lid is not closed.
It is also known to place gas leak detectors in kitchen stoves to prevent fire hazard when pilot lights are inadvertently distinguished.
While the prior art, as discussed above, has provided several solutions related to safety, it has not provided as much in the way of reducing inadvertent fuel loss. The safety systems which shut off gas supplies when the flame is inadvertently extinguished also save fuel as a side effect of their safety operation.
The foregoing prior art approaches are directed to problems which result from device malfunctions, such as loss of flame, flame detection, etc. They do not address the avoidance of problems which are caused by grills that are functioning correctly, but may cause problems due to being inadvertently left on by the user.
As a result, grills which are not malfunctioning, but which are inadvertently left on by a user, can cause fires by overheating the grill to the point where structures near the grill may be ignited. Likewise, if material is left in a grill by a user, that material may ignite and subsequently cause nearby structures to ignite due to overheating.
In addition to the safety hazards associated with unattended grills, the unattended operation of a grill also results in an economic cost to the user. It would be desirable to have a grill which could determine when a user is finished using the grill and automatically turn off the grill.
While the prior art has provided solutions related to safer operation of gas fueled grills, it has concentrated on detecting grill malfunctions such as flame out, gas leakage, etc, and avoiding problems caused by the malfunctions. Likewise, solutions provided by the prior art have been directed to remote ignition of grills to avoid injuries in the event of an explosion when the user is just beginning to use the grill. While, these solutions address the consequences of device malfunction, such as temporary loss of flame, gas leaks, etc., they have failed to provide a device which can avoid fire hazards and unnecessary fuel loss when the grill is not malfunctioning. In particular, the prior art has failed to provide a device which can determine, based on pattern of use, that a properly functioning grill has been inadvertently left on and then shut off the gas supply to avoid fire or fuel loss before they happen.